[Steve Bentley]

There was some ink and oil and water stock footage we used a while back that looks exactly like the displacement effect on Jared Harris’s face. (after working with the footage for a month it gets sort of burned in to your retinas and becomes recognizable in other spots when you see it). So it could be as simple as that.
There were a number of titles that used other stock ink effects over the years but I think every one got bored with the same patterns appearing over and over again. Then we started looking for other ways to do it.
We like Turbulence FD but you can get pretty much the same effects (to use as displacement elements) out of Blender (its the smoke generator).

[Steve Bentley]

I’ve run into something similar too. I’ve got an Animation Best file that is 6760×1080 (3x HD wide) that compresses to H264 just fine as long as the source is somewhere around 20gb and in the range of 30-40 seconds long. Now that I have a 32 gb file that is a little more than a minute, I get errors exporting out of QT (I’m on PC’s).
Media encoder won’t go anywhere near that pixel size (in any way i’ve tried).
If I have to I can go to Motion I can but I wondered if there was another solution.
I’m off to try FFMPG.

[Steve Bentley]

The Set Matte effect is actually a legacy effect from before Adobe owned AE. (that was the only way to do “track matte”s back then) But it’s still so useful for things, like you pointed out – to be able to matte things procedurally so users of the file don’t have to dig and you don’t have to worry about layer hierarchy.

The really great thing is that you can keep a layer’s original alpha (by selecting “comp matte with original” in the effect) and now you have technically two alpha’s at work: the layer you point to with the Set matte effect, and the layer’s own alpha from a rendered source or PShop (or if the layer is precomp with alpha info). You can then go one better by putting that layer with the setMatte effect below another and using track matte to triple matte the layer.

This of course could all be done by precomping the original and then just trackmatting the outer layer again, but often you want to preserve a blend/transfer mode (which can be lost with a precomp) or you have mixed 2D and 3D stuff going on and precomping suddenly sends your layer into the Forbidden Zone as the 3D camera tries to reposition it in a new WorldSpace. And yes, you can do some fancy “toWorld, fromWorld” stuff to reign that back in, but why bother?

[Steve Bentley]

And remember that first one in the list has an index of 0 not 1.
The indexing might also be flaky – I’ve done this a billion times and about a million times I’ve just rebuilt the nodes and links because what normally works, wasn’t. Thinking it was a carbon based error I saved the one that worked and the one that didn’t and forensically compared them. Identical.
So when you think you are doing it all right, you might just be.

[Steve Bentley]

Or it could just be the 2018 memory issue. Its finally become habit for us any time we see something odd in 2018 to just purge call caches and that solves the problem 50% of the time.
There is an update for 2018 but we haven’t seen an improvement in the cache issue.

[Steve Bentley]

If it’s a precomposed walk cycle inside another comp or if its footage, the best way probably is to use the enable time remapping (layer/time/EnableTimeRemapping – ETR).
With this you can set keyframes on any frame of the animation, and the keyframe IS that frame. So you could set one keyframe when the left foot comes down and then set another when it comes down at the end of the cycle. You then extend the layer’s length (which ETR lets you do) and then you can copy and paste those two keyframes anywhere you want down the length of the layer.
You could use a loop expression but that makes it harder to pause or ease in or bounce if you want your character to have a little less roboticness or if you want to speed up or slow down the motion (which you can do just by dragging the keyframes further apart. Want him to stop? No problem just make that keyframe a hold keyframe.
If the animation is a precomp there is no granularity to the “steps” so no matter how you stretch or ease the key frames the motion will always be smooth. If the animation is coming from another program as frames – try and render out a high FPS rate and then the ETR will have more frames to pick from when it starts scaling the speed.

[Steve Bentley]

There are lots of ways to achieve this. But if you are new to AE jumping into expressions right away might be daunting. (and that’s probably the best way to achieve all you want to.)
But here are some ready made scripts that can do the trick,
https://aescripts.com/easy-arrows/
https://aescripts.com/bao-boa/

BOA just does so many things and makes them pretty easy. Especially arrows. (I’m not affiliated with either of these).

[Steve Bentley]

There are so many ways to create that but in that example it looks like they have attached circles to the TrapCode Form plug in at each vertex and used the stock wiggle out of the box. Trapcode Particular could also do this.

[Steve Bentley]

The way some compressed files (like MP4) are encoded creates virtual frames (this is a gross oversimplification) . So if you are using these compressed files as source for your footage, AE can get stuck on these unusual frames.
If you can try exporting the Mp4 from quicktime or some other conversions software into a non compressed format – like animation Best or AVI uncompressed, then use that as your source in AE and see if it will render past that point.

[Steve Bentley]

Sure.
I’ve found you have to make a keyframe on your mask path before you do this next step( but it may not be necessary in some instances).
Then with that path selected in your timeline, under the Window menu select Create Nulls from Paths (mine is near the bottom of the list but you may also find it in the File/Scripts menu).
Then you have a choice – you can click nulls follow points or points follow nulls or trace path.
If you choose points follow nulls then each node along the path is linked to a null which is positioned right on top of where each node is. You can animate those nulls as you would any object with eases and keyframes or expressions.
Then you can just link your audio to those nulls either through expressions or copy and paste or pickwhips.